1. Field
Embodiments of the invention relate to communications networks and particularly to wireless communications networks. More specifically, embodiments of the invention relate to contention resolution in device-to-device (D2D) communications.
2. Description of the Related Art
Device-to-device (D2D) communication is expected to become a key feature of the future evolution of current 3rd Generation (3G) and beyond-3G wireless communication systems, such as long term evolution (LTE) and International Mobile Telecommunications Advanced (IMT-A) systems.
Long Term Evolution (LTE) refers to improvements of the Universal Mobile Telecommunications System (UMTS) through improved efficiency and services, lower costs, and use of new spectrum opportunities. UMTS Terrestrial Radio Access Network (UTRAN) refers to a communications network including base stations, or Node-Bs, and radio network controllers (RNC). UTRAN allows for connectivity between the user equipment (UE) and the core network. The RNC provides control functionalities for one or more Node Bs. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS).
LTE is a 3rd Generation Partnership Project (3GPP) standard that provides for uplink peak rates of at least 50 megabits per second (Mbps) and downlink peak rates of at least 100 Mbps. LTE supports scalable carrier bandwidths from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD). As mentioned above, LTE is also expected to improve spectral efficiency in 3G networks, allowing carriers to provide more data and voice services over a given bandwidth. Therefore, LTE is designed to fulfill future needs for high-speed data and media transport in addition to high-capacity voice support. Advantages of LTE include high throughput, low latency, FDD and TDD support in the same platform, an improved end-user experience, and a simple architecture resulting in low operating costs.
An IMT-A cellular system, sometimes referred to as a 4G system, is expected to have target peak data rates of up to 100 Mbit/s for high mobility, such as mobile access, and up to 1 Gbit/s for low mobility, such as local wireless access. IMT-A systems are expected to utilize frequency-domain equalization schemes, including multi-carrier transmission such as Orthogonal Frequency Division Multiple Access (OFDMA).
One area of endeavor with respect to D2D communication involves ensuring minimal or no signal interference among user terminals, while observing the constraints of network resources. For example, D2D communication can utilize or re-use the same resources within a cellular network, and, therefore, there is a need to coordinate the D2D and cellular communication to optimize the use of resources as to offer guaranteed service levels to the users in the cellular network and minimize the interference between the cellular users and D2D communication.